Charging control device

ABSTRACT

A charging control device includes a control unit and a monitoring unit. The control unit performs at least one of controlling charging to a rechargeable battery and monitoring a state of a rechargeable battery, while outputting a state signal which indicates an operation state of the control unit. The monitoring unit determines whether or not the operation state of the control unit is a predesignated specified operation state based on the state signal outputted from the control unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Patent Application No.2008-105775 filed Apr. 15, 2008 in the Japan Patent Office, thedisclosure of which is incorporated herein by reference.

BACKGROUND

The present invention relates to a charging control of a rechargeablebattery.

In recent years, a charger provided with a microcomputer for the purposeof achieving high functionality and efficiency is widely used as acharger for charging various rechargeable batteries such as a nickelhydride rechargeable battery and a lithium ion rechargeable battery. Inthe charger, the microcomputer controls battery charging based onvarious information inside the charger and also from a battery packincluding a rechargeable battery.

Not only the charger but also the battery pack including a rechargeablebattery is now being widely used which is provided with a microcomputerand the microcomputer monitors the state (for example, voltage,temperature and so on) of the rechargeable battery and performs variouscontrols based on various information (for example, voltage, temperatureand so on) of the rechargeable battery. As noted above, an enhancementof functionality is facilitated by providing a microcomputer in acharging system which charges a rechargeable battery by connecting abattery pack including the rechargeable battery to a charger.

In a case where a microcomputer controls generation of a chargingdirect-current power inside the charger or charging to a rechargeablebattery inside the battery pack, a software error caused in themicrocomputer (software anomaly) or hardware anomaly in themicrocomputer inhibits normal control by the microcomputer. Therechargeable battery may not be properly charged.

For example, there is a known charger provided with a microcomputer inwhich, when the microcomputer outputs a charging permission signal, aconverter operates to convert an external input power to a chargingdirect-current power, while, when a charging stop signal is outputtedfrom the microcomputer, the converter is inhibited from operating. Ifthe charging permission signal continues to be outputted from themicrocomputer due to anomaly in the microcomputer of the chargerconstituted as such, the rechargeable battery continues to be chargedregardless of its charged state.

The rechargeable battery may not be charged appropriately.

To solve the above problem, one technique is disclosed, for example, inUnexamined Japanese Patent Publication No. 2003-299260 in which thepower outputted from the converter is periodically turned off (for 10 msper second, for example) so as to superimpose a periodic pulse from themicrocomputer on the output voltage from the converter, and a watchdogcircuit detects the pulse superimposed on the output voltage from theconverter. If the pulse is not detected normally, the converter isstopped.

SUMMARY

In the above disclosed technique, whether or not the microcomputercontrols the converter normally is monitored based on the periodic pulsesuperimposed on the output voltage from the converter. Thus, the controlstate of the microcomputer can be monitored only when the output voltageis outputted from the converter to the rechargeable battery (that is,only during charging to the rechargeable battery).

Accordingly, even if some anomaly occurs to the microcomputer inside thecharger, for example, in a state where the rechargeable battery is stillconnected after being charged, the anomaly cannot be detected. Also, forexample, there may be a case where a charger is independently operatedin a state where the rechargeable battery is not connected but thecharger is connected to an external power source (for example, AC 100Vpower source). If anomaly occurs to the microcomputer in such state, theanomaly cannot be detected.

Regarding not only the microcomputer inside the charger but also thebattery pack provided with a microcomputer, the state monitoring,charging control and other various controls of a rechargeable batteryinside the battery pack may not be performed normally, if some kind ofanomaly occurs to the microcomputer inside the battery pack, even thoughthe microcomputer inside the charger functions normally. In the abovedescribed technique, the control state of the microcomputer inside thecharger can be only monitored while the battery is being charged. Inaddition, there is no way to monitor the control state of themicrocomputer inside the battery pack.

In one aspect of the present invention, it would be desirable thatwhether or not an operation state of a control unit involved in chargingcontrol of a rechargeable battery is a predesignated operation state canbe determined regardless of whether or not the rechargeable battery isbeing charged.

A charging control device in a first aspect of the present inventionincludes a control unit and a monitoring unit. The control unit performsat least one of controlling charging to a rechargeable battery andmonitoring a state of a rechargeable battery, while outputting a statesignal which indicates an operation state of the control unit. Themonitoring unit determines whether the operation state of the controlunit is a predesignated specified operation state based on the statesignal outputted from the control unit.

In the charging control device, the control unit not only performs atleast one of controlling charging to a rechargeable battery andmonitoring a state of a rechargeable battery, but also outputs a statesignal which indicates an operation state of the control unit.Accordingly, the monitoring unit can determine whether or not theoperation state of the control unit is the specified operation stateregardless of whether or not the rechargeable battery is being charged.

In other words, according to the first aspect of the present invention,it can be determined whether or not the operation state of the controlunit involved in charging control of the rechargeable battery is thespecified operation state regardless of whether or not the rechargeablebattery is being charged.

The control unit may output a signal of any form as the state signal.For example, the control unit may output pulse signals having a presetperiod as the state signal during operation of the control unit. Themonitoring unit may determine whether or not the operation state of thecontrol unit is the specified operation state based on the pulsesignals.

In this case, even if the configuration of the monitoring unit issimple, the monitoring unit can determine whether or not the operationstate of the control unit is the specified operation state.

The monitoring unit may determine whether or not the operation state ofthe control unit is the specified operation state based on anycharacteristics of the pulse signals. For example, the monitoring unitmay determine whether or not the operation state of the control unit isthe specified operation state based on the period of the pulse signals.

In case that the control unit is a computer, the charging control devicemay further includes a reset signal output unit that outputs a resetsignal to the computer to initialize the computer, when it is determinedby the monitoring unit that an operation state of the computer is thespecified operation state.

In this case, even if the operation state of the computer is changed tothe specified operation state, initialization of the computer canrelease the computer from the specified operation state.

The monitoring unit and the reset signal output unit may be configuredin any manner. For example, both the monitoring unit and the resetsignal output unit may be formed as one and the same watchdog timercircuit.

In such configuration, it is not necessary to separately provide themonitoring unit and the reset signal output unit in the charging controldevice. The configuration of the charging control device can besimplified.

The specified operation state can be any operation state, for example,an operation state defined in advance as an anomalous operation state.In this case, it is possible to determine whether the operation state ofthe control unit is an anomalous operation state.

The specified operation state may be an operation state defined inadvance as that it is inappropriate for the control unit to perform atleast one of controlling charging to the rechargeable battery andmonitoring the state of the rechargeable battery. In this case, it ispossible to determine whether the operation state of the control unit isan operation state inappropriate for the control unit to perform atleast one of controlling charging to the rechargeable battery andmonitoring the state of the rechargeable battery.

The charging control device may further includes a stop unit that stopscharging to the rechargeable battery when it is determined by themonitoring unit that the operation state of the control unit is thespecified operation state.

In the charging control device configured as such, charging to therechargeable battery is stopped when it is determined that the operationstate of the control unit is the specified operation state. Possibilitythat a trouble may occur to the rechargeable battery can be reduced.

The charging control device may be provided in a charging apparatus thatincludes a power converting unit that converts an externally suppliedexternal power to a charging power for charging the rechargeable batteryand outputs the converted charging power. In this case, the control unitmay control operation of the power converting unit to control chargingto the rechargeable battery, and the stop unit may stop output of thecharging power to the rechargeable battery when it is determined by themonitoring unit that the operation state of the control unit is thespecified operation state.

In such charging control device, regardless of whether or not the powerconverting unit is outputting charging power (whether or not therechargeable battery is being charged), determination can be made allthe time on whether or not the operation state of control unit is thespecified operation state. Moreover, when it is determined by themonitoring unit that the operation state of the control unit is thespecified operation state, the stop unit stops the output of thecharging power so as to reduce possibility that a trouble may occur tothe rechargeable battery.

The control unit may output to the stop unit an output control signalwhich selectively indicates one of permission and stop of the output ofthe charging power. In this case, the stop unit may selectively permitsand stops the output of the charging power to the rechargeable batterybased on the output control signal inputted from the control unit, whilestopping the output of the charging power to the rechargeable batteryregardless of indication of the output control signal when it isdetermined by the monitoring unit that the operation state of thecontrol unit is the specified operation state.

In the charging control device configured as such, the output of thecharging power can be permitted or stopped by the control unit. When itis determined that the operation state of the control unit is thespecified operation state, the output of the charging power can bestopped even though the control unit permits the output of the chargingpower.

The stop unit may stop the output of the charging power to therechargeable battery when a stop request signal is externally receivedwhich requests a stop of charging to the rechargeable battery. In thiscase, in response to the external request, charging to the rechargeablebattery can be stopped.

The external power may be a direct-current power or analternating-current power.

When the external power is an alternating-current power having apredetermined alternating-current voltage, the power converting unit mayinclude: a transformer that converts the alternating-current voltage ofthe external power; and an output smoothing circuit that generates thecharging power by smoothing the alternating-current power aftertransformed by the transformer.

In the case of the power converting unit configured as such, the stopunit may interrupt a current-carrying path from a power source of theexternal power to a rechargeable battery side through the transformerand the output smoothing circuit, when it is determined by themonitoring unit that the operation state of the control unit is thespecified operation state.

According to the charging control device configured as above,transformation of an alternating-current voltage of the external powercan be avoided, for example, by interrupting the current-carrying pathfrom the power source of the external power to the transformer tointerrupt input of the external power to the transformer. Also, forexample, output of the charging power can be interrupted by interruptingthe current-carrying path from the transformer to the output smoothingcircuit or from the output smoothing circuit to the rechargeablebattery.

The power converting unit may include a transformer that includes aprimary winding and a secondary winding. In the transformer, adirect-current power obtained from the external power may be inputted tothe primary winding. Also, the power converting unit may include aswitching element that is provided on a current-carrying path from anoutput source of the direct power to the primary winding forpermitting/interrupting the current-carrying path. Also, the powerconverting unit may include a switching control unit that generates analternating-current power in the secondary winding of the transformer byturning on/off the switching element. Moreover, the power convertingunit may include an output smoothing circuit that smoothes thealternating-current power generated in the secondary winding of thetransformer to generate the charging power. In the power converting unitconfigured as above, the stop unit may forcibly turn off the switchingelement when it is determined by the monitoring unit that the operationstate of the control unit is the specified operation state.

In the charging control device as such, when the operation state of thecontrol unit is the specified operation state, transformation by thetransformer is not performed and an alternating-current power is notgenerated on the secondary winding side of the transformer. Thus,generation of the charging power can be stopped. In other words,according to the charging control device, the output of the chargingpower to the rechargeable battery side from the charging apparatus canbe reliably stopped.

The stop unit may output to a battery pack containing the rechargeablebattery a stop request signal which requests to stop output to therechargeable battery of the charging power, when it is determined by themonitoring unit that the operation state of the control unit is thespecified operation state.

In this case, if the battery pack is configured to be able to stop theoutput of the charging power to the rechargeable battery in response tothe stop request signal, the output of the charging power to therechargeable battery can be stopped on the battery pack side.

The charging control device may be provided in a battery pack containinga rechargeable battery. In this case, the stop unit may stop output tothe rechargeable battery of a charging power for charging therechargeable battery, when it is determined by the monitoring unit thatthe operation state of the control unit is the specified operationstate.

In the charging control device as such, whether or not the operationstate of the control unit is the specified operation state can bedetermined all the time regardless of whether or not the rechargeablebattery is being charged. Moreover, when it is determined by themonitoring unit that the operation state of the control unit is thespecified operation state, the stop unit can stop the output of thecharging power thereby to reduce possibility that a trouble may occur tothe rechargeable battery.

In this case, the stop unit may interrupt a current-carrying paththrough which the charging power is outputted to the rechargeablebattery, when it is determined by the monitoring unit that the operationstate of the control unit is the specified operation state.

According to such charging control device, when the operation state ofthe control unit is the specified operation state, the output of thecharging power to the rechargeable battery can be reliably interrupted.

When the charging control device is provided in a battery packcontaining a rechargeable battery, the stop unit may output to acharging apparatus that charges the rechargeable battery a stop requestsignal for stopping the output of the charging power for charging therechargeable battery, when it is determined by the monitoring unit thatthe operation state of the control unit is the specified operationstate.

In this case, if the charging apparatus is configured to be able to stopthe output of the charging power in response to the stop request signal,the output of the charging power to the rechargeable battery can bestopped on the charging apparatus side.

Also, in this case, the stop unit may interrupt the charging poweroutputted from the charging apparatus to the battery pack, when it isdetermined by the monitoring unit that the operation state of thecontrol unit is the specified operation state.

According to the charging control device configured as such, when it isdetermined that the operation state of the control unit is the specifiedoperation state, a stop request signal is outputted to the chargingapparatus not only to stop the output of the charging power by thecharging apparatus, but also to interrupt the charging power in thebattery pack. Thus, possibility that a trouble may occur to therechargeable battery can be all the more reduced.

The control unit and the monitoring unit may be provided in a batterypack containing a rechargeable battery. The charging control device mayfurther includes a signal output unit that is provided in the batterypack and outputs to a charging apparatus that charges the rechargeablebattery a stop request signal that requests a stop of charging to therechargeable battery when it is determined by the monitoring unit thatthe operation state of the control unit is the specified operationstate. Also, the charging control device may further includes a stopunit that is provided in the charging apparatus and stops chargingoperation to the rechargeable battery by the charging apparatus inreceipt of the stop request signal.

In the charging control device configured as such, when the operationstate of the control unit inside the battery pack is the specifiedoperation state, the charging operation to the rechargeable battery bythe charging apparatus can be stopped by outputting the stop requestsignal to the charging apparatus from the battery pack. Thereby,possibility that a trouble may occur to the rechargeable battery can bereduced.

Alternatively, the control unit and the monitoring unit may be providedin a charging apparatus that outputs to a rechargeable battery acharging power for charging the rechargeable battery to charge therechargeable battery. The charging control device may further includes asignal output unit that is provided in the charging apparatus andoutputs to a battery pack containing the rechargeable battery a stoprequest signal that requests a stop of charging to the rechargeablebattery, when it is determined by the monitoring unit that the operationstate of the control unit is the specified operation state. The chargingcontrol device may further includes an interruption unit that isprovided in the battery pack and interrupts the charging power outputtedfrom the charging apparatus in receipt of the stop request signal.

In the charging control device configured as such, when the operationstate of the control unit inside the charging apparatus is the specifiedoperation state, the charging power outputted from the chargingapparatus can be interrupted in the battery pack side by outputting thestop request signal to the battery pack from the charging apparatus.Thereby possibility that a trouble may occur to the rechargeable batterycan be reduced.

A second aspect of the present invention is a charging apparatus thatcharges a rechargeable battery and includes the charging control deviceof the first aspect.

According to such charging apparatus, whether or not the operation stateof the control unit involved in charging control of the rechargeablebattery is the specified operation state can be determined regardless ofwhether or not the rechargeable battery is being charged.

A third aspect of the present invention is a battery pack that containsa rechargeable battery and includes the charging control device of thefirst aspect.

According to such battery pack, whether or not the operation state ofthe control unit involved in charging control of the rechargeablebattery is the specified operation state can be determined regardless ofwhether or not the rechargeable battery is being charged.

A fourth aspect of the present invention is a charging system thatincludes a battery pack containing a rechargeable battery and a chargingapparatus that charges the rechargeable battery, at least one of thecharging apparatus and the battery pack including the charging controldevice of the first aspect.

In the charging system, whether or not the operation state of thecontrol unit involved in charging control of the rechargeable battery isthe specified operation state can be determined in at least one of thecharging apparatus and the battery pack regardless of whether or not therechargeable battery is being charged.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described by way of example withreference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a charger and a battery pack whichconstitute a charging system of a first embodiment according to thepresent invention;

FIG. 2 is an electric diagram showing the charging system of the firstembodiment;

FIG. 3A is an explanatory view illustrating an example of watchdogpulses outputted from a control unit when the control unit is in anormal state;

FIG. 3B is an explanatory view illustrating an example of watchdogpulses outputted from the control unit when the control unit is in ananomalous state;

FIG. 3C is an explanatory view illustrating another example of watchdogpulses outputted from the control unit when the control unit is in ananomalous state;

FIG. 3D is an explanatory view illustrating further another example ofwatchdog pulses outputted from the control unit when the control unit isin an anomalous state;

FIG. 4 is a flowchart showing a charging control process executed by thecontrol unit according to the first embodiment;

FIG. 5 is a flowchart showing a control unit monitoring process executedby a watchdog timer IC of the first embodiment;

FIG. 6 is a block diagram showing a charging system of a secondembodiment;

FIG. 7 is an explanatory view showing a variation of a watchdog timercircuit and a charging permitting/stopping circuit; and

FIG. 8 is a block diagram showing a variation of the charging system ofthe second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment

A charging system 1 of the present embodiment shown in FIGS. 1 and 2includes a charger 10 and a battery pack 20 for charging a battery(rechargeable battery) used as a power source, for example, of anelectric power tool. The system is configured to charge a rechargeablebattery inside the battery pack 20 by the charger 10.

The charger 10 generates a charging power which is a direct-currentpower for charging the rechargeable battery inside the battery pack 20from a direct-current power from a cigarette lighter socket 2 (see FIG.2) provided in a not shown vehicle. A voltage of the direct-currentpower generated by the charger 10 of the present embodiment may not bestrictly constant and include a pulsating flow component. Moreparticularly, the charger 10 includes a cigarette lighter plug 15 to beconnected to the cigarette lighter socket 2 for inputting adirect-current power from the battery of the vehicle into the charger10. When the cigarette lighter plug 15 is inserted into the cigarettelighter socket 2 of the vehicle, a positive terminal 41 and a negativeterminal 42 (see FIG. 2) provided in the cigarette lighter socket 2 arerespectively connected to a positive terminal 34 and a negative terminal35 (see FIG. 2) provided in the cigarette lighter plug 15. As a result,a direct-current power is inputted into the charger 10 via a powersource cord 14.

On one end side of the top surface of the charger 10, a charging sideattachment portion 12 is formed to which the battery pack 20 isattached. A positive side charging terminal 36 (see FIG. 2) and anegative side charging terminal 37 (see FIG. 2) are provided at apredetermined position of the charging side attachment portion 12.

More particularly, the positive side charging terminal 36 and thenegative side charging terminal 37 are terminal for outputting adirect-current power to the battery pack 20. The positive side chargingterminal 36 and the negative side charging terminal 37 are covered by aprotection cover 16 on the top surface of the charging side attachmentportion 12. The protection cover 16 is movably provided in the charger10 in such a manner as to cover the positive side charging terminal 36and the negative side charging terminal 37 when the battery pack 20 isnot attached to the charging side attachment portion 12, while to exposethe positive side charging terminal 36 and the negative side chargingterminal 37 to the battery pack 20 when the battery pack 20 is attachedto the charging side attachment portion 12.

Moreover, the protection cover 16 covers at least one charging sidesignal terminal (not shown) for transmitting and receiving varioussignals between the charger 10 and the battery pack 20.

The charger 10 also includes a display portion 13 provided with aplurality of LEDs or the like for displaying an operation state of thecharger 10, a charged state of the battery pack 20 and so on, to theoutside.

On one side face of the battery pack 20, a battery side attachmentportion 22 is formed to which the charging side attachment portion 12 ofthe charger 10 is attached. At a predetermined position of the batteryside attachment portion 22, a positive side charging terminal 26 and anegative side charging terminal 27 are provided. The positive sidecharging terminal 26 and the negative side charging terminal 27 areterminals into which the charging power supplied from the charger 10 isinputted.

A signal terminal connector 28 is also provided in the battery sideattachment portion 22. Inside the signal terminal connector 28, at leastone battery side signal terminals (not shown) to be connected to theaforementioned at least one charging side signal terminal in the charger10 is provided.

When the battery side attachment portion 22 of the battery pack 20 isattached (fitted) to the charging side attachment portion 12 of thecharger 10, the positive side charging terminal 36 and the negative sidecharging terminal 37 in the charger 10 are respectively connected to thepositive side charging terminal 26 and the negative side chargingterminal 27 in the battery pack 20, as shown in FIG. 2. A charging powergenerated in the charger 10 is supplied to the rechargeable battery 23inside the battery pack 20 to charge the rechargeable battery 23.

The rechargeable battery 23 inside the battery pack 20 is an assembledbattery in which a plurality of battery cells are connected in series.Each of the battery cells of the present embodiment is a lithium ionrechargeable battery. Use of the lithium ion rechargeable batteries asthe rechargeable battery 23 is merely an example. Other types ofrechargeable batteries may be used.

In addition to the rechargeable battery 23, the battery pack 20 includesa control unit that monitors the state of the rechargeable battery 23, athermistor that detects a temperature of the rechargeable battery 23, anon-volatile memory (electrically rewritable) that stores variousinformation such as the charged state/charging history of therechargeable battery 23, and others. The battery pack 20 is configuredsuch that various operations including charging to the rechargeablebattery 23 are controlled by the control unit. Moreover, variousinformation such as the voltage, temperature and so on, of therechargeable battery 23 in the battery pack 20 are transmitted to thecharger 10 side via the above described at least one charging sidesignal terminal and at least one battery side signal terminal.

Upon supplying electric power of the battery pack 20 to a powerrecipient such as an electric power tool or the like, the battery sideattachment portion 22 is attached to a predetermined attachment portionof the electric power tool or the like as the recipient. As a result,electric power of the battery pack 20 (more particularly, electric powerof the internal rechargeable battery 23) is supplied to the electricpower tool or the like via the positive side charging terminal 26 andthe negative side charging terminal 27.

The battery pack 20 of the present embodiment is configured such thatthe positive side charging terminal 26, into which the charging power isinputted from the charger 10, is also used as a positive side poweroutput terminal when electric power is supplied to the power recipientsuch as an electric power tool or the like. This configuration is,however, only an example. A positive terminal when electric power issupplied to an electric power tool or the like may be additionallyprovided separately from the positive side charging terminal 26 forcharging.

As shown in FIG. 2, the charger 10 includes: a converter 3 that convertsa direct-current power inputted from the cigarette lighter socket 2 intothe above-described charging power of a predetermined voltage to beoutputted for charging the rechargeable battery 23 inside the batterypack 20; a control unit 7 that controls overall operation of the charger10 including the converter 3; a switching IC (SWIC) 4 that controlson/off of a switching FET 31 (later explained) composing the converter3; a charging permitting/stopping circuit 5 that permits or stops on/offcontrol of the switching FET 31 (and generation of the charging power)by the switching IC 4 according to a control signal (permission signalor stop signal) from the control unit 7; a switching IC control circuit6 that controls operation of the switching IC 4 according to a chargingcontrol signal from the control unit 7; a watchdog timer IC 8 thatmonitors the operation state of the control unit 7 based on watchdogpulses outputted from the control unit 7; and a constant voltage powersource circuit 9 that generates a control voltage for operating variouscircuits inside the charger 10.

The constant voltage power source circuit 9, when the direct-currentpower is inputted via the cigarette lighter plug 15, generates thecontrol voltage of a predetermined direct-current constant voltage fromthe inputted direct-current power. The constant voltage power sourcecircuit 9 of the present embodiment is configured to generate two typesof voltages: Vca (12 VDC, for example) and Vcb (5 VDC, for example), asthe control voltage. The voltages Vca and Vcb are respectively used foroperating various circuits and others inside the charger 10.

The converter 3 includes: an input smoothing capacitor C1 forrestricting voltage fluctuation in the direct-current power to beinputted; a transformer T1 for converting (transforming) adirect-current power into a predetermined alternating-current (AC)power; and a diode D1 and an output smoothing capacitor C3 for smoothingthe alternating-current power after converted by the transformer T1 to adirect-current power.

A direct-current power (positive) is inputted to one end of a primarywinding of the transformer 1. The other end of the primary winding isconnected to a drain of the switching FET 31.

The switching FET 31 is a FET as a so-called power semiconductorelement, in which a gate of the switching FET 31 is connected to a gatedriving circuit composed of two transistors Q1 and Q2, and others, asource of the switching FET 31 is connected to a ground line (grounded),which is a reference potential, and the drain of the switching FET 31 isconnected to the other end of the primary winding of the transformer T1as already described.

The gate driving circuit for driving the gate of the switching FET 31(and turning on/off the switching FET 31) includes: an input resistorR2; the NPN bipolar transistor Q1; the PNP bipolar transistor Q2; and aresistor R10 for gate bias. In the transistor Q1, a base of thetransistor Q1 is connected to the input resistor R2, the control voltageVca is applied to a collector of the transistor Q1 via a resistor R3,and an emitter of the transistor Q1 is connected to the gate of theswitching FET 31. In the transistor Q2, a base of the transistor Q2 isconnected to the input resistor R2, a collector of the transistor Q2 isconnected to a ground line (grounded) via a resistor R4, and an emitterof the transistor Q2 is connected to the gate of the switching FET 31.The bases of the respective transistors are connected to each other andso are the emitters. In other words, the gate driving circuit of thepresent embodiment is configured as a push-pull emitter follower circuitthat drives the gate of the switching FET 31 by the two transistors Q1and Q2.

The switching FET 31 is turned on/off by the switching IC 4 which inputsan on/off signal (a high level signal or a low level signal) to theinput side (the input resistor R2) of the above configured gate drivingcircuit. In other words, when a high level signal is outputted from theswitching IC 4, the transistor Q1 in the gate driving circuit is turnedon. Thereby, the switching FET 31 is turned on. When a low level signalis outputted from the switching IC 4, the transistor Q2 in the gatedriving circuit is turned on. Thereby, the switching FET 31 is turnedoff.

In this manner, the switching FET 31 is driven on/off by the gatedriving circuit according to the on/off signal from the switching IC 4.When the switching FET 31 is turned on/off as such, an intermittentelectric current (a type of alternating-current) flows into the primarywinding of the transformer T1. Thereby, an alternating-current power isgenerated on the secondary winding side. The alternating-current poweris smoothed by the output smoothing circuit composed from the diode D1and the output smoothing capacitor C3 to generate the charging power.The generated charging power is then outputted to the battery pack 20.

The switching IC 4 operates once the control voltage Vca is applied. Theoperation is controlled according to the charging control signal fromthe control unit 7. In other words, the switching IC 4, independentlyfrom an input port for the control voltage Vca for operation of theswitching IC 4, has a control port into which control information by thecontrol unit 7 is inputted. Into the control port, the control voltageVca is inputted via a resistor R13. The control port is connected to oneend (positive side) of a capacitor C2 of the switching IC controlcircuit 6 and a collector of a NPN bipolar transistor Q3.

The other end of the capacitor C2 and an emitter of the transistor Q3 ofthe switching IC control circuit 6 are connected to a ground line(grounded). An input resistor R6 and a base bias resistor R7 areconnected to a base of the transistor Q3. The other end of the inputresistor R6 is connected to a charging control signal output port of thecontrol unit 7.

The control unit 7 controls various operations inside the charger 10 asa whole. The control unit 7 of the present embodiment is a knownmicrocomputer. The control unit 7 operates once the control voltage Vcbis applied. The control unit 7 outputs the charging control signal tothe switching IC control circuit 6, the permission signal or the stopsignal to the charging permitting/stopping circuit 5, and the watchdogpulses to the watchdog timer IC 8. Also, when a predetermined conditionis satisfied in the watchdog timer IC 8, a reset signal is inputted fromthe watchdog timer IC 8 to the control unit 7. The control unit 7 isinitialized and restarted when the reset signal is inputted.

Not only inputs and outputs of the aforementioned signals, but also, forexample, various information inside the charger 10 such as the voltageand current of the charging power, various information inputted from thebattery pack 20 and so on, are inputted to the control unit 7. Variouscontrols are performed according to these input information.

The charging control signal inputted from the control unit 7 to theswitching IC control circuit 6 is a signal that controls generation ofthe charging power by the charger 10 and thus, charging to the batterypack 20. After the control unit 7 is started to operate, high levelsignals as charging control signals are outputted while battery chargingis not performed, that is, while a predetermined condition for batterycharging is not satisfied. In this case, in the switching IC controlcircuit 6, the potential of the collector of the transistor Q3 becomes aground potential since the transistor Q3 is turned on, and the potentialof the control port connected to the collector of the transistor Q3 inthe switching IC 4 also becomes the ground potential. In this case, theswitching IC 4 does not perform on/off control of the switching FET 31.

On the other hand, after the control unit 7 is started to operate andwhen the predetermined condition for charging to the battery pack 20 issatisfied, the control unit 7 outputs low level signals as the chargingcontrol signals. In this case, in the switching IC control circuit 6,the capacitor C2 is gradually charged by the control voltage Vca sincethe transistor Q3 is turned off, and the potential of the control portof the switching IC 4 becomes the same as the control voltage Vca.

Thereby, the switching IC 4 starts charging (generation/output of thecharging power) of the battery pack 20, assuming that a command to startbattery charging is issued by the control unit 7. In other words, byoutputting an on/off control signal to the gate driving circuit, theswitching FET 31 is turned on/off so as to generate the charging power.

In the present embodiment, the charging permitting/stopping circuit 5 isinserted to an output path of the on/off control signal from theswitching IC 4 to the gate driving circuit. The chargingpermitting/stopping circuit 5 operates according to the chargingpermission/stop signal from the control unit 7. When the permissionsignal is outputted as the charging permission/stop signal, the chargingpermitting/stopping circuit 5 activates the on/off control signal fromthe switching IC 4 to the gate driving circuit. When the stop signal isoutputted as the charging permission/stop signal, the chargingpermitting/stopping circuit 5 inactivates the on/off control signal fromthe switching IC 4 to the gate driving circuit.

The charging permitting/stopping circuit 5 mainly includes twotransistors: a transistor Q5 in which the charging permission/stopsignal from the control unit 7 is inputted to a base of the transistorQ5 via a resistor R11; and a transistor Q4 in which a collector of thetransistor Q5 is connected to a base of the transistor Q4. Thetransistor Q5 on the input side includes a base resistor and a biasresistor. An emitter of the transistor Q5 is connected to a ground line(grounded). The charging permitting/stopping circuit 5 also includes avoltage divider circuit. The voltage divider circuit includes: a voltagedivider resistor R8, to one end of which the control voltage Vca isapplied and the other end of which is connected to the collector of thetransistor Q5 on the input side (that is, to the base of the transistorQ4 on the output side); and a voltage divider resistor R9 connected tothe other end of the resistor R8 on one end and to a ground line on theother end.

In the above configured charging permitting/stopping circuit 5, when thepermission signal (high level signal) as the charging permission/stopsignal is inputted from the control unit 7 via the resistor R11, thetransistor Q5 on the input side is turned on. As a result, a collectorpotential of the transistor Q5, that is a base potential of thetransistor Q4 on the output side becomes low level and thus, thetransistor Q4 on the output side is turned off. Thereby, an impedance ofthe collector side of the transistor Q4 on the output side becomeshigh-impedance to a connection point of the resistors R1 and R2.Accordingly, the on/off control signal from the switching IC 4 istransmitted to the gate driving circuit via the resistors R1 and R2. Theswitching FET 31 is turned on/off according to the on/off controlsignal.

When the stop signal (low level signal) as the charging permission/stopsignal is inputted from the control unit 7 via the resistor R11, thetransistor Q5 on the input side is turned off. As a result, thecollector potential of the transistor Q5, that is the base potential ofthe transistor Q4 on the output side becomes a voltage division value ofthe control voltage Vca by the respective voltage divider resistors R8and R9 (voltage of the voltage divider resistor R9) and thus, thetransistor Q4 on the output side is turned on. Thereby, the potential ofthe collector of the transistor Q4 on the output side becomes low level(ground potential), that is, a connection point potential of theresistors R1 and R2 becomes the ground potential. Accordingly, theon/off control signal, even if transmitted from the switching IC 4, isnot transmitted to the gate driving circuit. The switching FET 31remains turned off.

In other words, the charging permitting/stopping circuit 5 permitson/off of the switching FET 31 by the switching IC 4 when the high levelpermission signal is inputted as the charging permission/stop signalfrom the control unit 7, while the charging permitting/stopping circuit5 disables on/off of the switching FET 31 by the switching IC 4 when thelow level stop signal is inputted as the charging permission/stopsignal.

Accordingly, the control unit 7 basically commands the switching IC 4 toperform battery charging by outputting the low level charging controlsignal to the switching IC control circuit 6 upon charging. Furthermore,by outputting the high level permission signal to the chargingpermitting/stopping circuit 5, the control unit 7 permits (activates)the on/off control of the switching FET 31 by the switching IC 4. As aresult, the switching FET 31 is turned on/off and the charging power isgenerated to be outputted to the battery pack 20. When stoppingcharging, the control unit 7 outputs the low level stop signal to thecharging permitting/stopping circuit 5 to stop (inactivate) the on/offcontrol of the switching FET 31 by the switching IC 4. Furthermore, byoutputting the high level charging control signal to the switching ICcontrol circuit 6, the control unit 7 disables the operation of theswitching IC 4 itself (output of the on/off control signal).

The control unit 7 also outputs watchdog pulses to the watchdog timer IC8 as previously described. The watchdog pulses are pulse signals nearlyperiodically outputted in the process of execution of a charging controlprocess program by the control unit 7. In other words, the chargingcontrol process program includes a process step to output the watchdogpulses in preset periods. The control unit 7, when turned on and startedto operate, executes the charging control process program at all timesduring its operation.

Accordingly, as long as the control unit 7 operates normally, thewatchdog pulses continue to be outputted from the control unit 7 inpreset periods. The watchdog pulses shown in FIG. 3A is an example ofthe watchdog pulses outputted when the control unit 7 is in a normalstate. The watchdog pulses shown in FIG. 3A are generated by repeatedlyexecuting, in a period T, a process step of setting an output voltage tohigh level (5V) for a given length of time and then setting the outputvoltage to low level for a given length of time.

The watchdog pulses illustrated in FIG. 3A have been explained to beoutputted in the constant period T. However, this does not necessarilymean that the watchdog pulses are (must be) outputted exactly in theperiod T. As described in the above, the watchdog pulses are outputtedby execution of the program. Thus, depending of the process speed andprocess steps or the like of the program execution, it is very likelythat the period of outputting the watchdog pulses is not consistent withthe period T (it is rather more difficult to strictly conform the periodof outputting the watchdog pulses to the period T). Thus, slightdeviation from the period T is acceptable. The watchdog pulses withinthe acceptable range are regarded as being outputted in the period T.

The watchdog timer IC 8 monitors whether or not the control unit 7operates normally based on the watchdog pulses outputted from thecontrol unit 7. Particularly, whether or not the watchdog pulses areoutputted normally from the control unit 7 is determined, for example bymeasuring elapsed time from when the voltage of the watchdog pulses isturned to high level last time until when the watchdog pulses are againturned to high level, and so on. Based on the determination result, theoperation state of the control unit 7 is monitored.

If the control unit 7 is in a normal state, the watchdog pulses areoutputted in the preset period T, as shown in FIG. 3A. Thus, thewatchdog timer IC 8 determines that the control unit 7 operates normallybased on the watchdog pulses. The reset signal to the control unit 7 isnot outputted (in other words, the reset signal is made to high level).

On the other hand, in the case of a software error caused in thecharging control process executed by the control unit 7 (softwareanomaly) or hardware anomaly in the control unit 7, generation of thecharging power may not be controlled normally. Thus, in the case ofanomaly in the control unit 7 as described in the above, the stop signal(low level) has to be transmitted to the charging permitting/stoppingcircuit 5 as the charging permission/stop signal so that batterycharging is stopped.

However, in the case of anomaly in the control unit 7, it is difficultfor the control unit 7 in itself to control its performance such asoutputting the stop signal to the charging permitting/stopping circuit 5due to the anomaly to itself. Thus, even though anomaly occurs to thecontrol unit 7 and battery charging should be stopped, the permissionsignal may continue to be outputted to the charging permitting/stoppingcircuit 5 from the control unit 7. Battery charging may be continued.

In the charger 10 of the present embodiment, the reset signal from thewatchdog timer IC 8 is outputted not only to the control unit 7 but alsoto the charging permitting/stopping circuit 5. The reset signal from thewatchdog timer IC 8 is inputted to the base of the transistor Q5 on theinput side of the charging permitting/stopping circuit 5, in the samemanner as the charging permission/stop signal inputted from the controlunit 7.

By such configuration, when the control unit 7 operates normally andbattery charging is performed, the charging permission/stop signal fromthe control unit 7 is the permission signal (high level). The resetsignal (low level signal) is not outputted from the watchdog timer IC 8to the charging permitting/stopping circuit 5. Battery chargingoperation is permitted. In the explanation below, the reset signal (lowlevel) from the watchdog timer IC 8 to be inputted to the control unit 7is referred to as a “first reset signal”, while the reset signal to beinputted to the charging permitting/stopping circuit 5 is referred to asa “second reset signal”.

As anomaly such as a software error occurs to the control unit 7 and thepermission signal from the control unit 7 continues to be outputted,battery charging operation by the charging permitting/stopping circuit 5continues to be permitted. However, if anomaly occurs to the controlunit 7 as such, the watchdog pulses are not outputted normally. Examplesof the watchdog pulses when the control unit 7 is in an anomalous stateare, as shown in FIGS. 3B-3D, a continuous low level state of thewatchdog pulses (FIG. 3B), a continuous high level state of the watchdogpulses (FIG. 3C), a state in which the watchdog pulses are outputtedonly in a period larger than the output period T of a normal time (thatis, the signals do not shift to high level even after the period T)(FIG. 3D), and so on.

Therefore, the watchdog timer IC 8, when it is determined that thewatchdog pulses are not outputted normally, that is, the control unit 7is not operating normally, based on the watchdog pulses, outputs thefirst reset signal to the control unit 7, and further outputs the secondreset signal to the charging permitting/stopping circuit 5.

When the second reset signal is inputted from the watchdog timer IC 8 tothe charging permitting/stopping circuit 5 as such, the transistor Q5 onthe input side is turned off even though the permission signal is stilloutputted from the control unit 7, because the second reset signal isinputted from the watchdog timer IC 8. As a result, the transistor Q4 onthe output side is turned on. The connection point potential of theresistors R1 and R2 becomes a ground potential. The battery charging isforced to be stopped.

When it is determined that the operation of the control unit 7 isanomalous, the watchdog timer IC 8 outputs the first reset signal to thecontrol unit 7 to initialize the control unit 7.

In case that the anomaly of the control unit 7 is, for example, causedby a software error and thus the permission signal is kept outputted,output of the first reset signal to the control unit 7 and thesubsequent initialization of the control unit 7 by the watchdog timer IC8 may restore the control unit 7 to a normal state.

However, the first reset signal may not be normally inputted to thecontrol unit 7 from the watchdog timer IC 8, for example, due to someanomaly in an input path of the first reset signal to the control unit 7from the watchdog timer IC 8 or, even if the first reset signal isnormally inputted, some anomaly may occur inside the control unit 7 andan initialization inside the control unit 7 may not be normallyperformed. Also, for example, even though the control unit 7 isinitialized, a software error may immediately occur once again andnormal charging may be unable to be performed. Accordingly, ifdetermination on whether or not to permit battery charging is leftindependently to the control unit 7, it is not always possible to stopbattery charging at the time when anomaly occurs to the control unit 7.

In the present embodiment, when the watchdog timer IC 8 determines thatsome anomaly has occurred to the control unit 7, the watchdog timer IC 8directly output the second reset signal to the chartingpermitting/stopping circuit 5 without involving the control unit 7. Inthis manner, battery charging is forced to be stopped regardless of thecharging permission/stop signal from the control unit 7.

Now, a charging control process executed by the control unit 7 and acontrol unit monitoring process executed by the watchdog timer IC 8 inthe charger 10 of the present embodiment constituted as above will beexplained by way of FIGS. 4 and 5.

The control unit 7, when the control voltage Vcb is applied to startoperation of the control unit 7, executes the charging control processshown in FIG. 4 on a steady basis during its operation.

When the process is started, first a watchdog timer (WDT) process isexecuted (S110). Particularly, in the WDT process, a high level signalis first outputted from a port for outputting a watchdog pulse. Afterelapse of a certain time period (Time Wait), a low level signal isoutputted and the elapse of the certain time period is awaited (TimeWait). In other words, the WDT process of S110 is a process ofoutputting the watchdog pulses for one period shown in FIG. 3A.

After the output of the watchdog pulses for one period, it is determinedwhether or not the battery pack 20 is attached (S120). The determinationis performed, for example, by the control unit 7 which determineswhether or not there is a connection with the thermistor circuit insidethe battery pack 20 based on an electric level of at least one chargingside signal terminal mentioned above.

Here, if the battery pack 20 is not yet attached (S120: NO), the processreturns to S110. If the battery pack 20 is attached (S120: YES), batterycharging is started (S130). In other words, the control unit 7 outputsthe low-level charging control signal to the switching IC controlcircuit 6 to instruct the switching IC 4 to start charging, and alsooutputs the permission signal (high-level signal) to the chargingpermitting/stopping circuit 5. As a result, on/off control of theswitching FET 31 by the switching IC 4, and generation/output of thecharging power, are started.

The WDT process is again performed in the same manner as in S110 tooutput the watchdog pulses for one period (S140). Moreover, is itdetermined whether or not the battery pack 20 is detached (S150). If thebattery pack 20 is detached from the charger 10 (S150: YES), a chargingstop process is performed (S200). The process returns to S110 again. Thecharging stop process facilitates output of the high-level chargingcontrol signal to the switching IC control circuit 6 and removes thecharging instructions to the switching IC 4. Also, a stop signal(low-level signal) is outputted to the charging permitting/stoppingcircuit 5 from the control unit 7.

When it is determined that the battery pack 20 is not yet detached inthe determination step of S150 (S150: NO), it is determined whether ornot the rechargeable battery 23 inside the battery pack 20 is fullycharged (S160). The determination can be performed, for example, basedon a detection value obtained by directly or indirectly detecting thevoltage of the rechargeable battery 23. If it is determined in thisdetermination step that the rechargeable battery 23 is not fully charged(S160: NO), the process returns to S140. If it is determined that therechargeable battery 23 is fully charged (S160: YES), a chargingcompletion process is performed (S170). The charging completion process,which is basically the same as the charging stop process in S200, stopsthe on/off control of the switching FET 31 by the switching IC 4 to stopthe battery charging operation.

After the charging completion process in S170, the WDT process isperformed again in the same manner as in S110 to output the watchdogpulses for one period (S180). Moreover, in the same manner as in S150,it is determined whether or not the battery pack 20 is detached (S190).If not (S190: NO), the process returns to S180. If the battery pack 20is detached (S190: YES), the process returns to S110.

As above, the control unit 7, when starting the operation, executes thecharging control process of FIG. 4 on a steady basis during itsoperation. Thereby, as long as the control unit 7 operates normally(that is, as long as the charging control process is performed normallyby the control unit 7), the watchdog pulses are periodically outputted,regardless of whether or not battery charging is being performed andwhether or not the battery pack 20 is attached.

Now, a control unit monitoring process executed by the watchdog timer IC8 will be explained using a flowchart of FIG. 5. The monitoring processto the control unit 7 based on the watchdog pulses by the watchdog timerIC 8 is performed by hardware (logic circuit) in practice. However, inthe present embodiment, the hardware process is replaced with aflowchart for the sake of easy understanding.

As the watchdog timer IC 8 starts the control unit monitoring process,it is first determined whether or not the watchdog pulses from thecontrol unit 7 are within a normal range, that is, whether or not thewatchdog pulses are outputted in the predetermined cycle T (S210). Thedetermination is performed by setting a permissible range to a certainextent. For example, when the elapsed time since the watchdog pulse hasbeen previously inputted exceeds the period T+a (a is a given value), itis determined that the watchdog pulses are not within the normal range.

When it is determined that the watchdog pulses are within the normalrange (S210: YES), the control unit 7 is considered operating normally.The output signal to the charging permitting/stopping circuit 5 is setto high level (S220). The process returns to S210. In other words, whilethe control unit 7 is in a normal state and the watchdog pulses areoutputted normally, the steps from S210-S220 are repeated.

On the other hand, when anomaly such as a software error occurs to thecontrol unit 7 and the watchdog pulses are not outputted normally (S210:NO), the watchdog timer IC 8 outputs the second reset signal to thecharging permitting/stopping circuit 5 (S230), and outputs the firstreset signal to the control unit 7 (S240). After standing by for acertain time period (S250), the process returns to S210.

As described in the above, the charging system 1 of the presentembodiment, the control unit 7 controls generation/output of thecharging power in the charger 10. When battery charging is performed,the control unit 7 outputs the low-level charging control signal to theswitching IC control circuit 6 to instruct the switching IC 4 to startcharging. Also, the control unit 7 outputs the high-level chargingpermission/stop signal (permission signal) to the chargingpermitting/stopping circuit 5 so that the battery charging is started.The watchdog timer IC 8 monitors the operation state of the control unit7 based on the watchdog pulses outputted in a certain period from thecontrol unit 7 while the control unit 7 operates normally. Whendetermining that the operation of the control unit 7 is anomalous, thewatchdog timer IC 8 outputs the first reset signal to the control unit 7and also output the second reset signal to the chargingpermitting/stopping circuit 5, thereby forcing to stop the batterycharging operation regardless of indication of the signal from thecontrol unit 7 to the charging permitting/stopping circuit 5.

According to the charging system 1 of the present embodiment, regardlessof whether or not the battery pack 20 is attached to the charger 10 andof whether or not the rechargeable battery 23 is being charged, thewatchdog timer IC 8 is able to monitor the operation state of thecontrol unit 7 at all times. When it is determined that the control unit7 is not operating normally, the watchdog timer IC 8 itself can directlyoutput the second reset signal to the charging permitting/stoppingcircuit 5 regardless of indication of the charging permission/stopsignal from the control unit 7 to the charging permitting/stoppingcircuit 5, in order to forcibly stop the battery charging operation.Thus, possibility that a trouble may occur to the rechargeable battery23 due to anomaly of the control unit 7 can be reduced. In other words,anomaly of the control unit 7 can be appropriately treated.

A particular method to forcibly stop battery charging at the time ofanomaly of the control unit 7 is to invalidate the on/off signal fromthe switching IC 4 to the switching FET 31. In other words, not that thecharging power is not outputted to the battery pack 20 side, butgeneration itself of the charging power is stopped. In this manner,output of the charging power to the battery pack 20 side can be reliablystopped.

Moreover, in the present embodiment, when anomaly occurs to the controlunit 7, the watchdog timer IC 8 forcibly stops the battery chargingoperation and resets the control unit 7. Thus, for example, in a case,such as anomaly by a software error, where mere initialization allowsrestoration of the control unit 7 to a normal state, the control unit 7can be immediately restarted even if falling in an anomalous state.Therefore, it is more effective.

Second Embodiment

Now, a charging system according to a second embodiment will beexplained by way of FIG. 6. A charging system 50 of the presentembodiment is different from the charging system 1 of the firstembodiment in that the supply source of the external power inputted to acharger 60 is an alternating-current power source 51 in the presentembodiment. Thus, a converter 61 of the charger 60 includes: an inputrectifying/smoothing circuit 62 that rectifies an alternating-currentpower from the alternating-current power source 51 to be converted to adirect-current power; a power converting circuit 63 that converts thedirect-current power from the input rectifying/smoothing circuit 62 toan alternating-current power having a predetermined alternating-currentvoltage; and an output smoothing circuit 64 that smoothes thealternating-current power converted by the power converting circuit 63to generate a charging power.

The power converting circuit 63 is identical to the portion in FIG. 2made up from the transformer T1, the switching FET 31 and the gatedriving circuit (transistors Q1, Q2 and so on). The output smoothingcircuit 64 is identical to the output smoothing circuit made up from thediode D1 and the output smoothing capacitor C3 in FIG. 2.

A battery pack 73 of the present embodiment includes: a control unit 71that monitors a state of the rechargeable battery 23 which is chargedwith the charging power inputted from the charger 60; a watchdog timerIC 72 that monitors an operation state of the control unit 71; and acharging permitting/stopping circuit 53 that, when it is determined bythe watchdog timer IC 72 that the control unit 71 is not operatingnormally, interrupts supply of the charging power to the rechargeablebattery 23.

The control unit 71 of the battery pack 73, as in the control unit 7inside the charger 60, outputs watchdog pulses on a steady basis all thetime during its operation as long as itself operates normally. Thewatchdog timer IC 72 inside the battery pack 73 monitors the operationstate of the control unit 71 in the same manner as the watchdog timer IC8 inside the charger 60 based on the watchdog pulses from the controlunit 71. When determining that the control unit 71 is not operatingnormally, the watchdog timer IC 72 outputs the first reset signal to thecontrol unit 71 to initialize the same and also outputs the second resetsignal to the charging permitting/stopping circuit 53.

The charging permitting/stopping circuit 53 of the battery pack 73 isprovided, inside the battery pack 73, on a current-carrying path (powerfeeding path) through which the charging power inputted from the charger60 is inputted to the rechargeable battery 23, and permits or interruptsthe current-carrying path. Particularly, while it is determined by thewatchdog timer IC 72 that the control unit 71 is operating normally, thecurrent-carrying path is permitted so that charging to the rechargeablebattery 23 is enabled. On the other hand, when it is determined by thewatchdog timer IC 72 that the control unit 71 is not operating normally,the watchdog timer IC 72 outputs the second reset signal. The secondreset signal urges the charging permitting/stopping circuit 53 tointerrupt the current-carrying path and to forcibly stop feeding of thecharging power to the rechargeable battery 23.

The charging permitting/stopping circuit 53 of the battery pack 73 maybe configured in any manner as long as the current-carrying path can bepermitted/interrupted depending on presence and absence of the secondreset signal from the watchdog timer IC 72.

Moreover, in the charging system 50 of the present embodiment, when thewatchdog timer IC 72 of the battery pack 73 determines that theoperation state of the control unit 71 is anomalous, the watchdog timerIC 72 not only outputs the second reset signal to the chargingpermitting/stopping circuit 53 of the battery pack 73, but also outputsthe second reset signal to the charging permitting/stopping circuit 65inside the charger 60. The charging permitting/stopping circuit 65inside the charger 60 is different from the charging permitting/stoppingcircuit 5 of the first embodiment only in that the second reset signalis inputted from not only the watchdog timer IC 8 inside the charger 60but also the watchdog timer IC 72 inside the battery pack 73. Thecharging permitting/stopping circuit 65 is the same as the chargingpermitting/stopping circuit 5 of the first embodiment in other parts.

The charging system 50 of the present embodiment is basically the sameas the charging system 1 of the first embodiment with respect to otherconfiguration. Accordingly, the same reference number as in the firstembodiment is given to the same component as that of the charging system1 of the first embodiment, and the description thereof is omitted.

In the charging system 50 of the present embodiment configured as above,the charger 60 monitors the operation state of the control unit 7 in thecharger 60 by the watchdog timer IC 8, in the same manner as in thecharger 10 of the first embodiment. When it is determined that thecontrol unit 7 is not operating normally, generation of the chargingpower is forcibly stopped by the second reset signal.

In addition, in the present embodiment, even inside the battery pack 73,the watchdog timer IC 72 monitors the operation state of the controlunit 71. If the watchdog timer IC 72 determines that the control unit 71is not operating normally, the current-carrying path (power feedingpath) to the rechargeable battery 23 inside the battery pack 73 isinterrupted by the second reset signal.

In this manner, the charger 60 and the battery pack 73 respectivelymonitor the operation state of the built-in control unit individually.When anomaly occurs, a predetermined operation is performed so as not tocharge the rechargeable battery 23.

Moreover, in the present embodiment, when the control unit 71 inside thebattery pack 73 is in an anomalous state, not only the current-carryingpath to the rechargeable battery 23 is interrupted by the chargingpermitting/stopping circuit 53 inside the battery pack 73, but alsogeneration of the charging power by the charger 60 is stopped.

According to the charging system 50 of the present embodiment, thewatchdog timer IC 72 can monitor the operation state of the control unit71 on a steady basis in the battery pack 73 as well, in the same manneras in the charger 60 (also in the same manner as in the charger 10 ofthe first embodiment), regardless of whether or not the charging to therechargeable battery 23 is performed. When it is determined that thecontrol unit 71 is not operating normally, the current-carrying path tothe rechargeable battery 23 is interrupted to forcibly and reliably stopthe charging.

When anomaly occurs to the control unit 71 inside the battery pack 73,the second reset signal is inputted to the charging permitting/stoppingcircuit 65 of the charger 60. Thereby, generation of the charging powerin the charger 60 itself is forcibly stopped. The charging to therechargeable battery 23 can be reliably stopped in response to anomalyof the control unit 71.

Variation

The embodiments of the present invention have been described in theabove. However, the present invention is not limited to theaforementioned embodiments but can take various modes without departingfrom the technical scope of the present invention.

For instance, in the charger 10 of the charging system 1 of the firstembodiment, when it is determined by the watchdog timer IC 8 that thecontrol unit 7 is in an anomalous state, the second reset signal isoutputted to the charging permitting/stopping circuit 5 so as toinvalidate the on/off control of the switching FET 31 by the switchingIC 4. However, the configuration of the watchdog timer IC 8 and theconfiguration of the charging permitting/stopping circuit 5 are notlimited to those described in the first embodiment. The watchdog timerIC 8 and the charging permitting/stopping circuit 5 can be configured,for example, as shown in FIG. 7.

In FIG. 7, a watchdog timer IC 81 is configured as a discreet circuit,and a charging permitting/stopping circuit 82 is configured topermit/interrupt a current-carrying path (power output path) to thebattery pack 20 side from the converter 3.

In other words, in the watchdog timer IC 81 of FIG. 7, when the watchdogpulses (high level) are inputted from the control unit 7, capacitors C21and C22 are charged. As the watchdog pulses become low level, theelectric charges for charging to the capacitor 21 are discharged via adiode D11 and a circuit (ground) inside the control unit 7. The electriccharges for charging to the capacitor C22 are inhibited from beingdischarged by a diode D12 and retained, but are little by littledischarged via a resistor R21. However, since the charging pace by thewatchdog pulses is much faster than the discharging pace, the chargingvoltage of the capacitor C21 is gradually increased each time thewatchdog pulses are outputted. Consequently, a FET 86 is turned on.

A source of the FET 86 is connected to a ground line. The controlvoltage Vcb is applied to its drain via a relay coil L11 inside thecharging permitting/stopping circuit 82. In the chargingpermitting/stopping circuit 82, a relay contact (a contact) 87 isarranged on an output path (current-carrying path on a positive side) ofthe charging power from the converter 3.

Accordingly, while the control unit 7 operates normally and the watchdogpulses are inputted normally from the control unit 7 to the watchdogtimer IC 81, the FET 86 is turned on in the watchdog timer IC 81 and therelay coil L11 is energized to turn on the relay contact 87.Accordingly, the charging power is supplied to the battery pack 20 side.

On the other hand, when anomaly occurs to the control unit 7 and thewatchdog pulses from the control unit 7 are not inputted normally to thewatchdog timer IC 81, the FET 86 is turned off in the watchdog timer IC81 and no electric current flows through the relay coil L11. As aresult, the relay contact 87 is turned off. Output of the charging powerfrom the converter 3 to the battery pack 20 side is forciblyinterrupted.

With respect to the battery pack 73 of the second embodiment as well,the watchdog timer IC 72 may be configured as the watchdog timer IC 81of FIG. 7, and the charging permitting/stopping circuit 53 may beconfigured as the charging permitting/stopping circuit 82 of FIG. 7.

In an example shown in FIG. 7, the charging permitting/stopping circuit82 is provided on the current-carrying path on the output side of theconverter 3. However, the charging permitting/stopping circuit 82 may beprovided on the current-carrying path on the input side of the converter3 so as to urge/interrupt input of an external power to the converter 3(input to the transformer T1).

Not only the charging permitting/stopping circuit 5 shown in the firstembodiment is provided inside the charger, but also the chargingpermitting/stopping circuit 82 shown in FIG. 7 may be provided insidethe charger. In this manner, at the time of anomaly of the control unit7, not only the on/off control of the switching FET 31 by the switchingIC 4 is forcibly invalidated to turn off the switching FET 31, but alsoa so-called current-carrying path for charging power leading from thecigarette lighter plug 15 to the positive side charging terminal 36 viathe converter 3 can be interrupted. Forcible termination of the batterycharging can be much ensured.

Also, in the charging system 50 of the above described secondembodiment, the second reset signal outputted from the watchdog timer IC8 of the charger 60 is inputted only to the charging permitting/stoppingcircuit 65 of the charger 60. However, the second reset signal outputtedfrom the watchdog timer IC 8 may be inputted to the chargingpermitting/stopping circuit 53 of the battery pack 73, as shown in FIG.8.

In the charging system 50 configured as above, when it is determined bythe watchdog timer IC 8 that the control unit 7 of the charger 60 is notoperating normally, not only the output of the charging power from thecharger 60 is stopped but also the current-carrying path from theconverter 61 of the charger 60 to the rechargeable battery 23 of thebattery pack 73 is interrupted.

In other words, when the control unit 7 of the charger 60 is notoperating normally, the output of the charging power to the rechargeablebattery 23 can be reliably stopped. Possibility that a trouble may occurto the rechargeable battery 23 can be all the more reduced.

1. A charging control device comprising: a control unit that performs atleast one of controlling charging to a rechargeable battery andmonitoring a state of a rechargeable battery, while outputting a statesignal which indicates an operation state of the control unit; and amonitoring unit that determines whether or not the operation state ofthe control unit is a predesignated specified operation state based onthe state signal outputted from the control unit.
 2. The chargingcontrol device according to claim 1, wherein the control unit outputspulse signals having a preset period as the state signal duringoperation of the control unit, and the monitoring unit determineswhether or not the operation state of the control unit is the specifiedoperation state based on the pulse signals.
 3. The charging controldevice according to claim 2, wherein the monitoring unit determineswhether or not the operation state of the control unit is the specifiedoperation state based on the period of the pulse signals.
 4. Thecharging control device according to claim 1, wherein the control unitis a computer, and the charging control device further comprises a resetsignal output unit that outputs a reset signal to the computer toinitialize the computer, when it is determined by the monitoring unitthat the operation state of the computer is the specified operationstate.
 5. The charging control device according to claim 1, wherein thespecified operation state is an operation state defined in advance as ananomalous operation state.
 6. The charging control device according toclaim 1, wherein the specified operation state is an operation statedefined in advance as that it is inappropriate for the control unit toperform at least one of controlling charging to the rechargeable batteryand monitoring the state of the rechargeable battery.
 7. The chargingcontrol device according to claim 1, further comprising: a stop unitthat stops charging to the rechargeable battery when it is determined bythe monitoring unit that the operation state of the control unit is thespecified operation state.
 8. The charging control device according toclaim 7, wherein the charging control device is provided in a chargingapparatus that includes a power converting unit that converts anexternally supplied external power to a charging power for charging therechargeable battery and outputs the converted charging power, thecontrol unit controls operation of the power converting unit to controlcharging to the rechargeable battery, and the stop unit stops output ofthe charging power to the rechargeable battery when it is determined bythe monitoring unit that the operation state of the control unit is thespecified operation state.
 9. The charging control device according toclaim 8, wherein the control unit outputs to the stop unit an outputcontrol signal which selectively indicates one of permission and stop ofthe output of the charging power, and the stop unit selectively permitsand stops the output of the charging power to the rechargeable batterybased on the output control signal inputted from the control unit, whilestopping the output of the charging power to the rechargeable batteryregardless of indication of the output control signal when it isdetermined by the monitoring unit that the operation state of thecontrol unit is the specified operation state.
 10. The charging controldevice according to claim 8, wherein the stop unit stops the output ofthe charging power to the rechargeable battery when a stop requestsignal is externally received which requests a stop of charging to therechargeable battery.
 11. The charging control device according to claim8, wherein the external power is an alternating-current power having apredetermined alternating-current voltage, the power converting unitincludes: a transformer that converts the alternating-current voltage ofthe external power; and an output smoothing circuit that generates thecharging power by smoothing the alternating-current power aftertransformed by the transformer, and the stop unit interrupts acurrent-carrying path from a power source of the external power to arechargeable battery side through the transformer and the outputsmoothing circuit, when it is determined by the monitoring unit that theoperation state of the control unit is the specified operation state.12. The charging control device according to claim 8, wherein the powerconverting unit includes: a transformer that includes a primary windingand a secondary winding and in which a direct-current power obtainedfrom the external power is inputted to the primary winding; a switchingelement that is provided on a current-carrying path from an outputsource of the direct power to the primary winding forpermitting/interrupting the current-carrying path; a switching controlunit that generates an alternating-current power in the secondarywinding of the transformer by turning on/off the switching element; andan output smoothing circuit that smoothes the alternating-current powergenerated in the secondary winding of the transformer to generate thecharging power, and the stop unit forcibly turns off the switchingelement when it is determined by the monitoring unit that the operationstate of the control unit is the specified operation state.
 13. Thecharging control device according to claim 8, wherein the stop unitoutputs to a battery pack containing the rechargeable battery a stoprequest signal which requests to stop output to the rechargeable batteryof the charging power, when it is determined by the monitoring unit thatthe operation state of the control unit is the specified operationstate.
 14. The charging control device according to claim 7, wherein thecharging control device is provided in a battery pack containing arechargeable battery, and the stop unit stops output to the rechargeablebattery of a charging power for charging the rechargeable battery, whenit is determined by the monitoring unit that the operation state of thecontrol unit is the specified operation state.
 15. The charging controldevice according to claim 14, wherein the stop unit interrupts acurrent-carrying path through which the charging power is outputted tothe rechargeable battery, when it is determined by the monitoring unitthat the operation state of the control unit is the specified operationstate.
 16. The charging control device according to claim 7, wherein thecharging control device is provided in a battery pack containing arechargeable battery, and the stop unit outputs to a charging apparatusthat charges the rechargeable battery a stop request signal for stoppingoutput of a charging power for charging the rechargeable battery, whenit is determined by the monitoring unit that the operation state of thecontrol unit is the specified operation state.
 17. The charging controldevice according to claim 16, wherein the stop unit interrupts thecharging power outputted from the charging apparatus to the batterypack, when it is determined by the monitoring unit that the operationstate of the control unit is the specified operation state.
 18. Thecharging control device according to claim 1 wherein the control unitand the monitoring unit are provided in a battery pack containing arechargeable battery, the charging control device further comprises: asignal output unit that is provided in the battery pack and outputs to acharging apparatus that charges the rechargeable battery a stop requestsignal that requests a stop of charging to the rechargeable battery whenit is determined by the monitoring unit that the operation state of thecontrol unit is the specified operation state; and a stop unit that isprovided in the charging apparatus and stops charging operation to therechargeable battery by the charging apparatus in receipt of the stoprequest signal.
 19. The charging control device according to claim 1,wherein the control unit and the monitoring unit are provided in acharging apparatus that outputs to a rechargeable battery a chargingpower for charging the rechargeable battery to charge the rechargeablebattery, the charging control device further comprises: a signal outputunit that is provided in the charging apparatus and outputs to a batterypack containing the rechargeable battery a stop request signal thatrequests a stop of charging to the rechargeable battery, when it isdetermined by the monitoring unit that the operation state of thecontrol unit is the specified operation state; and an interruption unitthat is provided in the battery pack and interrupts the charging poweroutputted from the charging apparatus in receipt of the stop requestsignal.